With the quick development of communication technologies, the Optical Transport Network (OTN), with the advantages of flexible scheduling and management of large capacity services, is increasingly becoming a major technology of the backbone transport network. In the OTN, client data is encapsulated into an Optical Channel Payload Unit (OPU), some overhead (OH) is added to the OPU to constitute an Optical Channel Data Unit (ODU), some OH and Forward Error Correction (FEC) is added into the ODU to constitute an Optical Channel Transport Unit (OTU), and is finally transmitted in the form of OTU.
With the rapid development of data services, more and more clients adopt Ethernet technology as the physical interface at the client side. It is foreseeable that in the coming years, the Ethernet services will keep a continuous high-speed growth. However, the current OTN technology is designed based on speech services such as synchronous digital hierarchy (SDH), and cannot well support the development trend of data services like Ethernet, thus studies are gradually carried out on the next generation of OTN network (NG OTN). The NG OTN is supposed not only to meet the requirements of services newly appeared, but also bear the current OTN. Thus, how to map a Lower Order Optical Channel Data Unit (LO ODU) to a Higher Order Optical Channel Data Unit (HO ODU) is a focus being discussed in the industry. The LO ODU may be regarded as ODUk (k=0, 1, 2, 2e, 3, 3e) existing in the current OTN, and herein represented as LO ODUk (k=0, 1, 2, 2e, 3, 3e). The HO ODU may be regarded as a data transmission unit of a higher rate, which belongs to the category of the NG OTN and is used for bearing the LO ODU, and the corresponding OPU is represented as HO OPUk (k=1, 2, 3, 3e, 4).
The conventional technical solution maps the standard ODUj (j=1, 2) (for 20 ppm bit tolerance) into the OPUk (k=2, 3) in an asynchronous manner. The asynchronous method maps the ODUj signal into the OPUk through an adjustment policy of −1/0/+1/+2. With the asynchronous manner, a maximum bit error tolerance between ODU1 and OPU2 is −113 to +83 ppm, a maximum bit error tolerance between ODU1 and OPU3 is −96 to +101 ppm, and a maximum bit error tolerance between ODU2 and OPU3 is −95 to +101 ppm.
However, the conventional method is not suitable for mapping the LO ODU into the HO ODU, e.g. for ODU2e (100 ppm bit tolerance), etc. ODUflex of higher bit tolerance may occur, and the adjustment policy of −1/0/+1/+2 does not meet the requirement for mapping the LO ODU into the HO ODU.